RFID (Radio Frequency Identification) transponders have been embedded in record members to track inventory. The data contained in the transponder is typically read by a stationary RFID read module as the inventory with the RFID transponder is carried past the stationary read module on a conveyor belt or the like. Similarly, stationary RFID write modules are typically used to write data into the RFID transponder. RFID printers are now required to be capable of both printing on record members, such as labels, tags etc., and capable of writing to and/or reading from a RFID transponder contained on the record member.
Currently, record members containing RFID transponders are encoded using printers having stepper motors. Typically, a web including record members is momentarily stopped so that the RFID transponder or inlay in a record may be encoded and the record member printed thereafter.
However, stopping of a web to encode a RFID transponder increases the amount of time for overall job completion and limits overall throughput of the printer. Therefore, there is a need in the art for an improvement to the printing and encoding of RFID record members particularly for record members being printed in batch processes.
In addition, in the printer depicted in application Ser No. 10/873,979, the printing position is where the print head could print on the record member. In the case of the depicted thermal printer, the printing position is at the nip where the print head cooperates with the platen roll and the record member. Printing occurs while the web is moving.
To print and RFID encode a relatively long record member, the print head can be at the printing position at the top of form or start of the record member adjacent its leading edge and printing can commence there or at a later time further from the leading edge of the record member. The movement of the web is stopped when the record member reaches the place where the transponder is to be RFID encoded. After RFID encoding, the printing of that record member can commence and continue until the web has advanced to the top of form position on the next adjacent upstream record member at which point the advance of the web ceases, and so on. With continued reference to relatively long labels, the next adjacent upstream record member was not encountered until after the record member has been completely printed and the print head has reached the top of form position of the next adjacent upstream record member, the print head is completely off the just printed and RFID encoded record member. Accordingly, none of the area of the record member is unprintable.
However, relatively short record members of, for example, one inch (2.54 cm) or less could be only partially printed and RFID encoded. Only part of the area of the record member could be printed because the distance between the antenna and the printing position is too great. Accordingly, while one relatively short record member has reached a position where its transponder can be RFID encoded, the print head is still on the immediately adjacent downstream record member. Accordingly, there can be no additional printing on the partially printed and RFID encoded downstream record member because it was not possible to print on one record member and RFID encode a different record member.
In addition, a prior art antenna design is detailed below in this background section along with the use of FIGS. 10-21. Improvements to the antenna design which correspond to various aspects of the following invention are described in the detailed description portion of this application. Further information on the prior art antenna design is described in co-owned U.S. application Ser. No. 10/873,979, filed Jun. 22, 2004 which is incorporated in its entirety.
With reference to FIG. 10, there is shown a prior art antenna system with an antenna assembly generally indicated at 540 disposed in the printer 40 (FIG. 1) between the web guide 62 (FIG. 1) and the platen roll 63. The antenna assembly 540 is mounted on a conductive shield 501. An inclined portion 503′ of a section 501′ has two laterally spaced holes 541 (only one of which is shown). The holes 541 are aligned with threaded holes 548. The antenna assembly 540 has an electrically conductive metal enclosure or shield generally indicated at 542 having side panels or side walls 543, 544, 545 and 546 and bottom or back panels 547. While the conductive shield 542 is composed of metal, the shield 542 can be constructed of molded or fabricated non-conductive plastics material which has a conductive coating such as would be created by vacuum metalizing or plating, wherein the plating is in conductive contact with the shield 501 and antenna 550. The enclosure 542 can also be constructed of a conductive plastics material, if desired. The side panels 543 through 546 terminate at an open top 542′. One bottom panel 547 has the threaded holes 548. The panels 547 are closely spaced or they can touch each other and constitute a back wall or back panel. Screws 549 pass through respective holes 541 and are threaded into the threaded holes 548 to hold the antenna assembly 540 securely and electrically connected to the inclined portion 503′ of the shield 501. The shield portion 503′ supports the antenna assembly 540 so that a microstrip or microstrip antenna 550, discussed below, is generally parallel to the web C and the plane of the RFID transponder T. The enclosure 542 is electrically grounded to the metal printer frame 72 through the shield 501.
With reference to FIGS. 10, 11 and 13, the prior art antenna assembly 540 includes the microstrip antenna 550 and the shield 542. The antenna assembly 540 is shown in FIG. 1 to be located at the write and/or read station. The shield 542 acts to direct the energy radiated from the antenna 550 to the region above opening 542′. This reduces the energy that is seen by the RFID transponders T located upstream and downstream from the RFID transponder located over or adjacent to the antenna 550. The shield 542 is electrically connected to conducting elements 553, 554 and 560 by screws 571 received in through plated-through holes 557 and threaded holes 570 (FIG. 17). The elements 553 and 560 are electrically connected to each other by plated-through holes 558. The conductive elements 553, 554, 556 and 560 are formed on a non-conducting substrate 552. The driven element of the antenna 550 is the microstrip 556. The resonant frequency of the antenna 550 is mainly determined by the length of the microstrip 556. The antenna assembly 540 is mounted on the shield portion 503′, with the plane of the microstrip antenna 550 being parallel to the web C. The main part of the antenna 550 is the driven element 556, the length of which is selected to be approximately a quarter wavelength of the desired resonant frequency of the antenna. The plane of the antenna 550 is shown to be generally parallel to the web C and the microstrip element 556 extends parallel to and in the same direction as the generally flat chip-containing transponder T in the web C. If desired, the antenna assembly 540 can be used to write to and/or read a transponder T which is at a different orientation such as perpendicular to the element 556, as contrasted to the parallel orientation of the transponder T shown in FIG. 2. The top of the shield or enclosure 542 or the opening 542′ is nominally spaced from the web C by 3.0 millimeters. The upper surface or first face of the antenna 550 is spaced 5.62 millimeters from the top of the enclosure or opening 542′. Microstrip antenna 550 parameters such as resonant frequency, bandwidth and driving point impedance can be changed by changing the length of element 556, the size and dielectric constant of the substrate 552, the width of element 556, and distance between holes 558 and 559. The beam width of the antenna assembly 540 is determined mainly by the position of the antenna 550 in the enclosure 542. The antenna 550 is operable in the ultra high frequency (UHF) range. Element 556 is 41.5 millimeters long and 5 millimeters wide, providing resonance at 915 MHz and broad band operation. The shield 542 also functions as a support or housing for the antenna 550.
With reference to FIG. 12, there is shown what can be described as a first face of the antenna 550, with FIG. 13 showing the second face. The antenna 550 is comprised of a printed circuit board 551 having the non-conductive substrate 552 with conductive portions or elements generally indicated at 553, 554 and 560. The conductive portions 553 and 554 preferably have peripheral edges or a boundary spaced inwardly from the side edges of the substrate 552 so they cannot contact the inside surfaces of the shield 542. The conductive portion 553 has a generally rectangular portion or element 555 with a narrow strip or driven element 556 extending from the rectangular conductive portion 555 toward but spaced from the portion 554. It is noted that the antenna of this embodiment can be formed without the conductive portion 554. The rectangular portion 555 of the portion 553 and the portion 554 have conductively plated-through holes 557, one of which is illustrated in greater detail in FIG. 17. The area 555 has four small, spaced, conductively plated-through holes 558 and the element 556 has one small, conductively plated-through hole 559, as shown in an enlarged scale in FIGS. 14 and 18. In this preferred embodiment, the hole 559 is 5.0 millimeters from the centerline of the holes 558 and the centerline of the holes 558 is 1.5 millimeters from the place where the element 556 joins the portion 555.
FIG. 13 shows that the second face is plated with a conductor 560, except for the marginal edges 561 and an area 562 best shown in FIG. 15. The conductor 560 forms a ground plane that extends substantially throughout the second face of the substrate 552, underlying the strip 556. This ground plane contributes to the directivity of the energy radiated from the strip 556 toward the transponder T. The conductor-free marginal edge 561 prevents the conductor 560 from contacting the inside surfaces of the shield 542. By spacing the elements 554, 555 and 560 from the enclosure 542, it assures that the only electrical connection of the antenna 550 to the enclosure 542 is through the screws 571. This assures that the characteristics of the antenna 540 are not affected by contact of elements 553, 554 and/or 560 with the conductive enclosure 542 at one or more other locations. A conductive area generally indicated at 563 is completely surrounded by conductor-free area 562. The conductive area or conductor 563 has a generally circular conductive portion 564 joined by a conductive bridge 566 to a generally circular conductive portion 565 which surrounds the plated-through hole 559. It is apparent that the conductive portion 565 is electrically connected to the microstrip element 556 through the plated-through hole 559 as best shown in FIG. 18.
With reference to FIGS. 16 and 20 through 21, the shield or enclosure 542 is shown to be comprised of a single piece of conductive metal such as aluminum, bent into the shape illustrated. With reference to FIG. 11, the panel 544 has a bent end portion 567 which overlaps the outside of the panel 546. The panel 544 has a hole 544′ through which the cable 577 passes. The spaced bottom panels 547 are joined to the side panels 543 and 544 at bends 568. Bent-in tabs 569 have threaded holes 570. The antenna 550 is supported by the tabs 569. As best shown in FIG. 17, one of the screws 571 extends through a star washer 572 and the plated-through hole 557 and is threaded into the hole 570 in the tab 569. The screws 571 insure that the conductive portions 554, 555 and 560 make good electrical contact with the tabs 569 which are part of the shield 542.
With reference to FIGS. 18 and 19, there is shown a jack generally indicated at 573 and a plug 574 connected thereto, however, FIG. 19 shows only the end of the jack 573. The jack 573 is of the surface-mount type and has four short square pins or feet 575 and has a short central pin 576 electrically isolated from body 577 and the pins 575 of the jack 573. Further details of the jack 573 and the plug as disclosed in specification sheets of Johnson Components, Waseca, Minn. entitled “MMCX-50 Ohm Connectors” and MMCX Straight Jack Receptacle, Surface Mount. The pin 576 of the plug 574 is connected to a conductor 577′ of the cable 577 as shown by dot-dash line 578. The conductor 577′ is electrically insulated from a braided shielding conductor 579 by insulation 580. The cable 577 is electrically insulated from contact with other printer parts by an insulator 581. The conductor 579, the body 582 of the plug 574, the body 577 of the jack 573, and the pins 573 are all connected electrically, and the plug 574 and the jack 573 are mechanically snap-connected.
The four pins 575 of the jack 573 are soldered to the copper-plated conductor 560, and the pin 576 is soldered to the circular portion 564 of the conductor 563. With reference to FIG. 15, the position of the four pins 575 is shown by phantom line squares 575P. A circuit path exists between the pin 576 and the conductor portion 556 through the conductor 563 and the plated hole 559.
By way of further example, not limitation, the substrate 552 is 18 millimeters in width, 95 millimeters in length and 1.57 millimeters in thickness; the enclosure or shield 542 is 104 millimeters in length from the outside of the wall 545 to the outside of the wall 546, 20.7 millimeters in width from the outside of the wall 543 to the outside of the wall 544, and 34 millimeters in height from the outside of the wall provided by panels 547 and the opening 542′; the thickness of bent sheet metal that comprises the panels 543, 544 545, 546, and 547 is 1.2 millimeters; the distance from the web guide 60 and the platen roll 63, namely the space available for the antenna assembly 500 or the antenna assembly 540 is about 24.65 millimeters; and the distance from the microstrip element 556 to the inside surface of the bottom panels 547 is 27.18 millimeters. The distance from the nip between the print head 69 and the platen roll 63 to terminal end of the guide 510 (FIG. 10) is 8 millimeters.
The following additional patent documents and other literature are made of record and may or may not be prior art: U.S. Pat. Nos. 4,408,906; 5,524,993; 5,833,377; 6,246,326; 7,180,627; 7,190,270; U.S. Publication No. 2001/0029857; U.S. Publication No. 2004/0100381; U.S. Publication No. 2005/0116034; U.S. Publication No. 2005/0274800; U.S. Publication No. 2005/0280537; U.S. Publication No. 2006/0104689; U.S. Publication No. 2006-0221363; Abstract of Japan Publication No. 2003-140548; Abstract of Japan Publication No. 2004-110994; Abstract of Japan Publication No. 2005-107991; Abstract of Japan Publication No. 2005-186567; Abstract of Japan Publication No. 2006-000936; Abstract of Japan Publication No. 2007-213298; Abstract of Japan Publication No. 2006-004150; and Abstract of Japan Publication No. 2008-124356.